1. Field of the Invention
The present invention relates to a stereoscopic image display device, and in particular, it relates to a stereoscopic display device suitable for performing a stereoscopic image display in a television, a video, a computer monitor, a game machine and the like.
2. Related Background Art
From among stereoscopic image display devices known heretofore, there has been a stereoscopic image display device using a parallax barrier or a lenticular lens as a display device capable of a stereoscopic observation without using a special eyeglass.
According to these methods, a synthetic image obtained by a plurality of parallax images corresponding to a plurality of observing points, respectively is displayed on an image display screen, and an emitting direction of an image information light from each of the parallax images is controlled by the parallax barrier or the lenticular lens arranged in front of the image display screen so as to allow each of the parallax images to be emitted with a different directivity borne, thereby presenting each of the parallax images to different observational regions. An observer recognizes a stereoscopic image by a parallax borne by the parallax image by placing the left and right observing eyes on the different observing regions without using the special eyeglass.
In such a stereoscopic image display device, in case a plurality of parallax images are synthesized, it is a common practice that each of the parallax images is divided into a longitudinal stripe shape, and the longitudinal stripe including different parallax images is horizontally arranged periodically so as to synthesize a synthetic image, and moreover, the parallax barrier and the lenticular lens are also made into the longitudinal stripe shape.
On the other hand, disclosed-in Japanese Patent Application Laid-Open No. H08-331605 and Japanese Patent Application Laid-Open No. H09-15549 are methods of using a synthesized image, which further divide the above-described synthesized image of the longitudinal stripe shape into a horizontal direction, and performs an arrangement laterally shifted according to the position in a vertical direction. FIG. 74 is an explanatory drawing of a pixel arrangement in Japanese Patent Application Laid-Open No. H08-331605, and FIG. 75 is an explanatory drawing of a parallax barrier aperture portion arrangement in the publication.
In FIG. 74, an individual rectangular region marked with an alphabet and a number is an individual pixel, and the alphabet indicates a type of color filter corresponding to a pixel, and the numbers 21 to 24 indicate the parallax images corresponding to each of the first to fourth observing points.
In the meantime, FIG. 75 shows the arrangement of an aperture (white portion) of the parallax barrier and a light shielding portion (shaded portion). As shown in FIG. 74, the pixel representing each of the parallax images is arranged in a matrix shape, in correspondence to which the aperture of the parallax barrier is arranged in the matrix shape.
FIG. 76 shows how the parallax image corresponding to the first observer's eye looks like from among the parallax images observed in case of using the pixel arrangement of FIG. 74 and the parallax barrier of FIG. 75. As evident from FIG. 76, in case the arrangement of the matrix shape is used, it is possible that a pixel representing a parallax image is dispersed in a longitudinal direction and in a lateral direction. In case an ordinary longitudinal stripe arrangement is used, the arrangement is characterized in that, while the pixel displaying a certain parallax image generates only laterally reduction of an image quality continuously in a longitudinal direction, the reduction of the image quality is hardly remarkable by using the above-described arrangement of the matrix shape.
On the other hand, it is disclosed in Japanese Patent Application Laid-Open No. H09-15549 that a modified lenticular lens can be used in place of the above-described parallax barrier. FIG. 77 shows the modified lenticular lens disclosed in Japanese Patent Application Laid-Open No. H09-15549. FIG. 78 shows how the parallax image corresponding to the first observer's eye looks like from among the parallax images observed in case of using the pixel arrangement of FIG. 74 and the modified lenticular lens of FIG. 77. As evident from FIG. 78, in case the arrangement of the matrix shape and the modified lenticular lens are used, the pixel displaying a parallax image is observed dispersed in a longitudinal direction and a lateral direction, and at the same time, each pixel is displayed enlarged in a lateral direction.
However, even when the above-described pixel arrangement of the matrix shape is used, as evident from FIG. 76, in case the parallax barrier is used, a region, which becomes a non-display region that is an umbra when observed from a certain observing position, largely emerges. That is, similarly to the conventional ordinary parallax barrier, in case the stereoscopic image display observable from the above-described four observing points is performed, the number of the pixels displaying a certain parallax image becomes one fourth. A ratio of display region is reduced in proportion to the number of observing points, and the non-display region is enlarged, and therefore, there arises a problem that brightness seems to be reduced for the observer's eye when the number of observing points is increased. Further, in case a color display is performed, a black region between the pixels displaying different colors is increased, and therefore, a color displayed by mixed colors is shifted to a blacker side than its original color, and there arises a problem that a correct display of a color becomes difficult.
Further, in case the modified lenticular lens is used, a ratio of non-display region becomes small compared to a case where the parallax barrier is used, but each pixel is widened in a lateral direction only so that a difference of resolution between the longitudinal direction and the lateral direction becomes large, and an apparent decrease of resolution becomes intensified.
An object of the present invention is to solve the above-described problems and provide a stereoscopic image display device, which does not generate a non-display region when an observer observes each of parallax images despite the device being a stereoscopic image display device for displaying a multi-observing point image.